What’s Wrong With This Picture?

I have posted this picture of Quincy's City Hall a few times over the past few months usually to announce the holiday schedule for the city. Yesterday, I looked at it carefully and noticed that there is something wrong with it. So let's have some fun. Can you see what is wrong? The answer has nothing to do with the windows which have been replaced since the picture was taken. If you know let me know. I will reveal the answer on Monday's Y101 Radio Morning show at 7:25 a.m.